Impeller for centrifugal fan and centrifugal fan

ABSTRACT

There is provided an impeller for a centrifugal fan which rotates around an axis extending from one side to the other side. The impeller includes a main plate, a plurality of blades each having one side portion located at the one side and the other side portion located at the other side, the one side portion being connected to a first surface of the main plate, and a connecting ring which connects the other side portions of the blades. A first circumferential groove to which a first balance weight is attachable is formed in an outer circumferential portion of a second surface of the main plate facing toward the one side. A second circumferential groove to which a second balance weight is attachable is formed in the connecting ring. An annular raised portion is formed on the first surface at a portion corresponding to the first circumferential groove.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent Application No. 2014-233618 filed on Nov. 18, 2014 and titled “IMPELLER FOR CENTRIFUGAL FAN AND CENTRIFUGAL FAN”, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present teaching relates to an impeller for a centrifugal fan and a centrifugal fan, in particular, to an impeller for a centrifugal fan and a centrifugal fan each having a structure wherein blades of the impeller are connected to each other with a connecting ring.

2. Description of the Related Art

A centrifugal fan has been widely used for cooling, ventilation, and air conditioning of various devices such as home appliances, OA devices and industrial devices, and as air fans for vehicles, and the like. A centrifugal fan of this kind is provided with an impeller including a disc-shaped main plate to which a driving shaft is fixed at a central portion of the main plate, and a plurality of curved blades (vanes) fixed on a surface of the main plate. Japanese Patent Application Laid-open No. 2014-088787 discloses this type of the centrifugal fan having such a structure that a connecting ring is fixed to the end portions on the outer circumferential (peripheral) side of the respective blades and which connects the blades with each other.

Note that this kind of fan is provided with a mechanism for suppressing any rotational imbalance generated in the impeller; Japanese Patent Application Laid-open No. 2014-088787 describes that the rotational balance of the impeller can be ensured by providing a thickness-reduction section on the connecting ring (paragraph [0105]). As a generally known method for adjusting the rotational balance of the impeller, a balance weight cancelling the rotational imbalance is attached to the impeller at a circumferential location axisymmetric (symmetric with respect to the rotational center of the impeller) to the location where a rotational imbalance is present. Japanese Patent Application Laid-open No. H11-210690 describes a turbo fan having a structure in which a clip-shaped balance weight is clamped and attached to the outer circumferential (peripheral) edge of a bell mouth corresponding to the connecting ring of Japanese Patent Application Laid-open No. 2014-088787.

SUMMARY

In the above methods for adjusting the rotational balance in the conventional fan, the adjustment of the rotational balance cannot be performed easily and quickly. Therefore, the mass production of the impeller and fan is time-consuming.

The present teaching has been developed considering the above situation, and a main object of the present teaching is to provide an impeller for a centrifugal fan capable of performing the adjustment of rotational balance easily and quickly and having excellent mass productivity, and to provide a centrifugal fan using such an impeller.

According to the first aspect of the present teaching, there is provided an impeller for a centrifugal fan which rotates around an axis extending from one side to the other side, the impeller including: a main plate; a plurality of blades each having one side portion located at the one side and the other side portion located at the other side, the one side portion being connected to a first surface of the main plate; and a connecting ring configured to connect the other side portions of the plurality of blades, wherein a first circumferential groove to which a first balance weight is attachable is formed in an outer circumferential portion on a second surface of the main plate, the second surface facing toward the one side; a second circumferential groove to which a second balance weight is attachable is formed in the connecting ring; and an annular raised portion is formed on the first surface of the main plate, at a location corresponding to the first circumferential groove.

According to the second aspect of the present teaching, there is provided an impeller for a centrifugal fan, including: a disc-shaped main plate; a plurality of blades arranged on a first surface of the main plate; and a connecting ring connecting end portions of the blades located at a side farther from the main plate;

wherein a first circumferential groove is formed in an outer circumferential portion of a second surface of the main plate, the second surface being opposite to the first surface; and a second circumferential groove is provided in the connecting ring.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view of a centrifugal fan related to an embodiment of the present teaching.

FIG. 2 is a plane view of an impeller provided on the centrifugal fan.

FIG. 3 is an upper side perspective view of the impeller.

FIG. 4 is a bottom side perspective view of the impeller.

FIG. 5 is a cross-sectional view showing a circumferential groove formed in the main plate.

FIG. 6 is a cross-sectional view showing a circumferential groove formed in the connecting ring.

EMBODIMENTS

In the following, an embodiment related to the present teaching will be explained with reference to the drawings.

<1. Basic Structure of Centrifugal Fan>

FIG. 1 is a vertical cross-sectional view of a centrifugal fan 1 provided with an impeller 3 related to an embodiment, FIG. 2 is a plane view of the impeller 3, and FIGS. 3 and 4 are upper and bottom side perspective views of the impeller 3, respectively. The centrifugal fan 1 is provided with a plate-shaped base 2, the impeller 3, and a motor 4 causing the impeller 3 to rotate.

In FIG. 1, the base 2 is depicted as a plate-shaped member placed horizontally. The impeller 3 is rotatably supported on the base 2 via a bearing 23. The impeller 3 has a disc-shaped main plate 31 arranged parallel to the base 2, a plurality of blades (vanes) 32 formed on the upper surface (a first surface) of the main plate 31, and a connecting ring 33 arranged along the outer peripheral portions of the blades 32. The impeller 3 is produced, for example, by integrally molding the main plate 31, the plurality of blades 32 and the connecting ring 33 with a synthetic resin.

As depicted in FIG. 1, the impeller 3 has the upper surface serving as a fluid inlet port 301 and the side circumferential (peripheral) surface serving as a fluid outlet (discharge) port 302, and the impeller 3 is rotated by the motor 4 in a direction indicated by an arrow R in FIG. 2. When the impeller 3 is rotated, air (fluid) is sucked from the fluid inlet port 301 and the air is discharged from the fluid outlet port 302. The air is discharged in a direction away from a shaft 34 fixed to the center of the impeller 3.

As depicted in FIG. 1, a cup-shaped hub section 311 having a cylindrical portion 312 and a lid portion 313 is formed in a central portion of the main plate 31. The hub section 311 protrudes upward from a flat portion of the main plate 31 which surrounds the hub section 311, and the motor 4 is accommodated inside the hub section 311. An upper end portion of the shaft 34, which extends in the up and down direction penetrating through the motor 4, is fixed to a central portion of the lid portion 313 of the hub section 311. The shaft 34 is coaxially fixed to the hub section 311 by, for example, the insert molding such that the shaft 34 is coincident (coaxial) with the central axis of the cylindrical portion 312 of the hub section 311. A boss 21 is formed at a central portion of the base 2, and a sleeve 22 extending in the up and down direction is upstandingly fixed inside the boss 21. Further, the shaft 34 is rotatably supported inside the sleeve 22 via a pair of upper and lower bearings 23. The bearings 23 are not limited to rolling bearings; sliding bearings such as oil retaining bearings (oilless bearings) may be used as the bearings 23.

As depicted in FIG. 2, each of the blades 32 is provided to be inclined relative to the radial direction of the impeller 3 such that an end portion on the outer peripheral side and an end portion on the inner peripheral side of the blade 32 are located at mutually different positions in the rotational direction of the impeller 3, and each of the blades 32 is curved to project toward the outer side in the radial direction of the impeller 3. With this, the plurality of blades 32 provides a spiral form as a whole. A gap is defined between the end portions on the inner peripheral side of the blades 32 and the cylindrical portion 312 of the hub section 311. The blades 32 are arranged to protrude on the main plate 31 at equal intervals (distances) therebetween in the circumferential direction, and the blades 32 are formed to have a height greater than the height of the hub section 311. The respective blades 32 are connected to one another by the connecting ring 33. In some cases, the height of the blades 32 is set to be smaller than the height of the hub section 311.

The connecting ring 33 is shaped to have an annular form connecting upper end portions (end portions opposite to the end portions at which the blades are connected to the main plate 31) of the respective blades 32, located on the outer peripheral side of the blades 32, and is shaped to protrude outwardly from the respective blades 32 further toward the outer side in the radial direction of the impeller 3. As depicted in FIG. 1, the connecting ring 33 is connected to each of the blades 32 via a connecting portion 331, and the inner diameter of the connecting ring 33 is set to be same as or greater than the outer diameter of the main plate 31. By setting the relationship between the inner diameter of the connecting ring 33 and the outer diameter of the main plate 31 in such a manner, a mold (metal mold) for shaping the impeller 3 can be formed as a two-piece structure having a movable side part and fixed side part. As a result, the cost of manufacturing the impeller 3 can be lowered, with an increased productivity as well.

As depicted in FIG. 1, the motor 4 which drives the rotation of impeller 3 is composed of a stator 41 fixed to the outer circumferential surface of the sleeve 22, and a rotor magnet 42 fixed to the inner circumferential surface of the cylindrical portion 312 of the hub section 311 such that the rotor magnet 42 faces the stator 41 with a gap. A yoke 421 is fixed on the outer circumferential side of the rotor magnet 42. The stator 41 is composed of stator cores 411 extending radially from the sleeve 22 toward the rotor magnet 42, insulators 412 attached to the stator cores 412 respectively, and coils 413 wound around the insulators 412 respectively. A circuit board 414 controlling the rotational drive of the impeller 3 is arranged at the lower side of the stator 41.

In the motor 4, the electric current controlled by a driving circuit of the circuit board 414 is made to flow in the coil 413 via the circuit board 414, and the stator cores 411 are successively excited. With this, the impeller 3 to which the rotor magnet 42 is fixed is rotated about the shaft 34 in the direction indicated by the arrow R in FIG. 2. When the impeller 3 is rotated, the plurality of blades 32 is rotated integrally to thereby generate the following blowing action. That is, the air is sucked from the fluid inlet port 301 located at the upper side of the impeller 3 and the air is discharged from the fluid outlet port 302 located at the lateral side of the impeller 3.

<2. Mechanism for Adjusting Rotational Balance>

Next, an explanation will be made about a mechanism for adjusting the rotational balance of the impeller 3. As depicted in FIG. 5, a circumferential groove (first circumferential groove) 314 which is open downward and extends in full circumference is formed on the lower surface (a second surface, a surface facing toward one side in the axial direction) of the main plate 31 of the impeller 3 in the outer circumferential portion (i.e. a portion defined on the outside of the middle position between the outer and inner circumferences, in the radial direction of the main plate 31) of the main plane. On the other hand, as depicted in FIG. 6, a circumferential groove (second circumferential groove) 334 which is open upward and extends in full circumference is formed on the upper surface (a surface facing toward the other side in the axial direction) of the connecting ring 33.

As depicted in FIG. 5, an annular raised portion 315 along the circumferential groove 314 is formed in the main plate 31 at a location above the circumferential groove 314 (on the other side in the axial direction). Thickness 315 t of the raised portion 315 is set to be same as or thinner than thickness 31 t of the main plate 31.

According to the impeller 3 related to the embodiment, balance weights W having an appropriate weight can be attached to the inside of either or both of the circumferential groove 314 of the main plate 31 and the circumferential groove 334 of the connecting ring 33, as depicted in FIGS. 5 and 6. By doing so, the rotational balance is adjusted. A clay-like material, such as putty, which has the plasticity and stickiness (adhesiveness) at a time of the attachment, and which can be cured after the attachment is appropriately used as the balance weight W. In a case of using the putty, by using a tool such as a spatula to embed an appropriate amount of the putty into the circumferential grooves 314 and/or 334, the putty can be attached to the circumferential grooves 314 and/or 334 without allowing the putty from extruding from the circumferential grooves 314 and 334.

In this embodiment, since the respective circumferential grooves 314 and 334 to which the balance weights W can be attached are arranged in the outer circumferential portions of the impeller 3, the rotational balance of the impeller 3 can be achieved effectively by a smaller amount of the balance weights W than in a case of attaching the balance weights W at any inner circumferential portions of the impeller 3. Further, since each of the circumferential grooves 314 and 334 is arranged at the outer circumferential portions of the impeller 3 and the surrounding portion around each of the circumferential grooves 314 and 334 is free (any other structure is not present around each of the circumferential grooves 314 and 334), the operation for attaching the balance weights W to the grooves can be performed easily. As a result, the rotational balance of the impeller 3 can be performed easily and quickly, thereby achieving an excellent mass productivity for the impeller 3. Furthermore, since the raised portion 315 is formed in the main plate 31 at the location corresponding to the circumferential groove 314, i.e., at the back of circumferential groove 314, the thickness of the portion of the impeller 3 at which the circumferential groove 314 is formed does not become thin, and thus the strength of this portion is ensured.

Moreover, since the inner diameter of the connecting ring 33 is set to be greater than the outer diameter of the main plate 31, the balance weight W can be attached to the circumferential groove 334 of the connecting ring 33 at a location farther from the rotational center of the impeller 3 than a conventional impeller, thereby further reduction in the amount of the balance weight W can be realized. Further, since the thickness 315 t of the raised portion 315 formed in the main plate 31 at the position above the circumferential groove 314 is set to be same as or less than the thickness 31 t of the main plate 31, it is possible to suppress any excessive protrusion of the raised portion 315 while ensuring the strength provided by the raising portion 315.

Furthermore, in the circumferential groove 314 of the main plate 31, an inner circumferential wall portion 314 a and an outer circumferential wall portion 314 b which compose the circumferential groove 314 are arranged as follows. That is, as depicted in FIG. 5, the inner circumferential wall portion 314 a is inclined relative to the radial direction (the lower surface of the main plate 31) at an angle α and the outer circumferential wall portion 314 b is inclined relative to the radial direction (the lower surface of the main plate 31) at an angle β, where the angle β is approximately 90 degrees (right angle) and the angle α is smaller than 90 degrees, for example, in a range of about 40 degrees to about 50 degrees. Note that, as depicted in FIG. 5, the angle α means the angle defined between the inner circumferential wall portion 314 a and a portion of a line extending along the main plate 31 in the radial direction of the main plate 31, the portion being defined on the outer side of the inner circumferential wall portion 314 a. Further, the angle β means the angle defined between the outer circumferential wall portion 314 b and a portion of the line extending along the main plate 31 in the radial direction of the main plate 31, the portion being defined on the inner side of the outer circumferential wall portion 314 b. By setting the angles α and β in such a manner, the width of the circumferential groove 314 becomes large, and thus the balance weight W such as the putty can be easily attached to the circumferential groove 314. At the same time, any separation of the balance weight W from the circumferential groove 314 caused by the centrifugal force can be suppressed.

Note that the circumferential groove 334 of the connecting ring 33 may also be similarly formed such that the inclination angle of an outer circumferential wall portion relative to the radial direction (the upper surface of the connecting ring 33) is greater than the inclination angle of an inner circumferential wall portion relative to the radial direction (the upper surface of the connecting ring 33). Further, pockets may be formed in each of the circumferential grooves 314 and 334 by providing partition walls which divide the internal annular space defined in each of the circumferential grooves 314 and 334 in the circumferential direction to thereby define the pockets. In each of the circumferential grooves 314 and 334 having this configuration, it is possible to suppress any displacement of the balance weight W in the circumferential direction, as the balance weight W is attached between the partition walls. Furthermore, the circumferential groove formed in the connecting ring 33 may be formed at radially outside location in relation to the blades 32.

According to the impeller related to the embodiment, the rotational balance can be adjusted by arranging and attaching the balance weight into each of the first circumferential groove of the main plate and the second circumferential groove of the connecting ring. Since the first circumferential groove of the main plate is formed in the outer circumferential portion of the main plate, the rotational balance can be adjusted effectively and with a smaller amount of the balance weight than in a case of attaching the balance weight in inner circumferential portion of the main plate. Further, the first circumferential groove is formed in the outer circumferential portion of the surface of the main plate on one side in the axial direction, the second circumferential groove is formed in the connecting ring connecting the other end portions of the blades, and the first and second circumferential grooves are both opened outward in the axial direction (any other structure is not present at the outer side in the axial direction of each of the first and second circumferential grooves). Thus, an operation for attaching the balance weights to the grooves respectively can be performed easily. As a result, the impeller related to the embodiment is capable of realizing the adjustment of rotational balance easily and quickly and has excellent mass-productivity. Further, since the annular raised portion is formed in the main plate at a portion corresponding to the first circumferential groove, the thickness of the portion is not thinned and the strength in the portion can be secured.

In the impeller related to the embodiment, since the connecting ring is arranged on the radial outer side of the plurality of blades, the amount of the balance weight to be attached to the second circumferential groove formed in the connecting ring can be made small.

In the impeller related to the embodiment, the circumferential groove has a large width. Thus, in a case that the balance weight is a clay-like material having plasticity, an operation for attaching the balance weight to the outer circumferential wall portion of the circumferential groove with a spatula or the like can be performed easily. In addition, since the balance weight is pressed against the outer circumferential wall portion by the centrifugal force, any separation of the balance weight from the circumferential groove can be suppressed.

In the impeller related to the embodiment, the balance weight attached to the circumferential groove of the connecting ring can be attached farther from the rotational center of the impeller, as compared with a conventional impeller, thereby contributing to reduce the amount of the balance weight.

In the impeller related to the embodiment, it is possible to avoid an excessive protrusion (projection) of the raised position while assuring the strength by the presence of the raised portion.

According to the present embodiment, an impeller for a centrifugal fan capable of adjusting the rotational balance easily and in a short time, and having excellent mass productivity can be provided, as well as a centrifugal fan using such an impeller can be provided. 

What is claimed is:
 1. An impeller for a centrifugal fan which rotates around an axis extending from one side to the other side, the impeller comprising: a main plate; a plurality of blades each having one side portion located at the one side and the other side portion located at the other side, the one side portion being connected to a first surface of the main plate; and a connecting ring configured to connect the other side portions of the plurality of blades, wherein a first circumferential groove to which a first balance weight is attachable is formed in an outer circumferential portion on a second surface of the main plate, the second surface facing toward the one side; a second circumferential groove to which a second balance weight is attachable is formed in the connecting ring; and an annular raised portion is formed on the first surface of the main plate, at a location corresponding to the first circumferential groove.
 2. The impeller for the centrifugal fan according to claim 1, wherein the main plate has a cup-shaped hub section protruding toward the other side; and a shaft is fixed to the hub section.
 3. The impeller for the centrifugal fan according to claim 1, wherein the connecting ring is provided on an outer side of the plurality of blades in a radial direction of the impeller, and connects surfaces of the blades located on the outer side in the radial direction.
 4. The impeller for the centrifugal fan according to claim 1, wherein the second circumferential groove is formed on a surface of the connecting ring facing toward the other side.
 5. The impeller for the centrifugal fan according to claim 1, wherein the second circumferential groove is formed on an outer side of the plurality of blades in a radial direction of the impeller.
 6. The impeller for the centrifugal fan according to claim 1, wherein at least one of the first circumferential groove of the main plate and the second circumferential groove of the connecting ring has an inner circumferential wall portion and an outer circumferential wall portion; the inner circumferential wall portion is inclined relative to a radial direction of the impeller at an angle α; the outer circumferential wall portion is inclined relative to the radial direction at an angle β; and the angle α is smaller than the angle β.
 7. The impeller for the centrifugal fan according to claim 1, wherein an inner diameter of the connecting ring is greater than an outer diameter of the main plate.
 8. The impeller for the centrifugal fan according to claim 1, wherein a thickness of the raised portion in the main plate is same as or less than a thickness of the main plate.
 9. A centrifugal fan comprising the impeller according to claim
 1. 10. An impeller for a centrifugal fan, comprising: a disc-shaped main plate; a plurality of blades arranged on a first surface of the main plate; and a connecting ring connecting end portions of the blades located at a side farther from the main plate; wherein a first circumferential groove is formed in an outer circumferential portion of a second surface of the main plate, the second surface being opposite to the first surface; and a second circumferential groove is provided in the connecting ring.
 11. The impeller according to claim 10, wherein an annular raised portion is provided on and projecting from the first surface of the main plate; and the annular raised portion is provided at a back of the first circumferential groove.
 12. The impeller according to claim 11, wherein a thickness of the raised portion in the main plate is not larger than a thickness of the main plate.
 13. The impeller according to claim 10, wherein the plurality of blades are connected by the connecting ring on an outer circumference side of the main plate.
 14. The impeller according to claim 10, wherein the second circumferential groove is provided on the connecting ring on a surface located on a farther side from the first surface of the main plate.
 15. The impeller according to claim 10, wherein a partition wall is provided inside of at least one of the first and second circumferential grooves to partition at least one of the first and second circumferential grooves in the circumferential direction.
 16. The impeller according to claim 10, wherein at least one of the first circumferential groove and the second circumferential groove has an inner circumferential wall portion and an outer circumferential wall portion; the inner circumferential wall portion is inclined relative to a radial direction of the main plate at an angle α; the outer circumferential wall portion is inclined relative to the radial direction at an angle β; and the angle α is smaller than the angle β. 